The present invention relates to a device and a method of using the device to heat up a chemical process vessel, such as a reactor, to control the temperature in a chemical process vessel or to maintain the temperature therein. Conventionally, chemical process reaction vessels which are used in thermal, usually exothermic processes, can be refractory lined and have been heated to operating temperature by passing preheated fuel gas through the reactor for a time sufficient to heat the refractory lining in the reactor. With this method, the heat transfer is inefficient, with only a small percentage of the heat energy from the preheated gas stream being transferred to the wall of the vessel. Electrical heating of the outer shell is another method of heating such a reactor. This may be accomplished by wrapping the outside of the vessel with an electrical jacket consisting of a series of high resistance heater coils. Still another conventional method of heating a chemical reactor is to wrap the outside of the reactor with a series of coils in a heating jacket to carry hot fluids thereby also relying on inefficient heat transfer mechanisms to supply the necessary heat.
All of the forgoing methods suffer from inefficiencies; including poor heat transfer, excessive cost, the need to provide reactors made from high temperature resistant metals and the requirement of having to purge an incompatible heating gas from the reactor prior to introducing the chemical reactants. U.S. Pat. No. 3,823,003 teaches the use of electrical heating of a vacuum furnace utilizing alternating current flowing along an outer steel shell of a reactor and then through a graphite brick lining back to the power source. This may lead to overheating of the outside of the metal reactor thereby posing a hazardous situation.
It is therefore one object of the present invention to provide an apparatus for heating a reactor that is efficient, safe and economical. It is another object of the present invention to provide an apparatus for heating a pressurized reactor, and it is still another objective to provide an apparatus that overcomes safety concerns associated with heating chemical reactors. A still further object is to provide a method for heating chemical process vessels utilizing the novel apparatus of the present invention.